Art of gelatinizing or colloiding low-viscosity colloids



Patented Oct. 8, 1940 UNITED STATES PATENT OFFICE ART or GELATINIZING R COLLOIDING LOW-VISCOSITY COLLOIDS No Drawing. Application August 21, 1937, Serial No. 160,316

Claims.

This invention relates to the art of gelatinizing or colloiding low-viscosity colloids, that is, colloids characterized by their tendency to form solutions of comparatively low viscosity when treated with a solvent or gelatinizing liquid. It deals more particularly with the treatment of fabrics or other bodies containing low-viscosity colloids in a manner designed to gelatinize or colloid thoroughly the colloid content of the 10 fabrics or other bodies while avoiding the creation therein of a low-viscosity colloid solution.

In accordance with the present invention, a low-viscosity colloid or a fabric or other body associated with low-viscosity colloid is treated with a solvent or gelatinizing liquid in the presence of an inhibitor of the development of a lowviscosity solution. I have determined that such principle of inhibiting the development of a low-v viscosity colloid solution when gelatinizing the i colloid content of a fabric or other body with a solvent or gelatinizing liquid is a most valuable one when the solvent-treated fabric or other body is to be molded, united to another surface, or otherwise manipulated in such a Way that a low-viscosity colloid solution would be displaced therefrom .to 'an undesirable degree. Thus, the use of an inhibitor of the development of a lowviscosity solution is of considerable utility when a box-toe blank or stiffener containing low-viscosity colloid as the stiffening medium is being conditioned with a solvent or gelatinizing liquid preparatory to being inserted into the shoe upper and lasted together with the upper, as in such case the development of a low-viscosity colloid solution would be attended under lasting pressure by undesirable exudation of the colloid solution from the stiffener blank into the neighboring upper parts and possibly also staining all the way through the upper.' Again, the use of such a 40 solvation-inhibitor is of value when a tape or other fabric coated with low-viscosity colloidal adhesive is to be adhesively activated with a solvent or gelatinizing liquid and then applied in activated state under some pressure to another surface and it is important that there be minimum flow or displacement of adhesive solution away from the work or surfaces being united.

Despite the fact that low-viscosity colloids orcoating operation. Thus, in producing shoe-stiflener material by impregnating a fabric with a stiffening colloid of the nature of nitrocellulose,

into the fabric bodyin a single impregnating treatment the desiredlarge amount of nitrocellulose as the stiifeningimpregnant. Contrariwise, the use of a solution of high-viscosity nitrocellulose in producing an impregnated fabric of high nitrocellulose content requires repeated impregnation with such solution, for the solution must be prepared at comparatively low nitrocellulose content in order to possess the appropriate impregnating fluency and a single impregnation of the fabric with the solution results in the deposit of only a fraction of the high nitrocellulose content to be realized in the finished shoe-stiifener material. Nevertheless, it, is undesirable to produce shoe-stiffener material containing low-viscosity nitrocellulose by reasonof the fact that when a shoe-stiffener is conditioned for lasting or shaping together with the shoe upper by treatment with nitrocellulose solvent, a low-viscosity nitrocellulose solution is regenerated in the stiffener blank and such lowviscosity nitrocellulose solution tends, especially under lasting pressure, to be displaced undesirably from the base fabric of the stiffener to the other shoe parts. By applying the principles of the present invention, however, and using the appropriate inhibitor of the development of lowviscosity nitrocellulose solution in the solvent liquid employed for conditioning the shoe stiffener, it becomes possible to gain the benefits incident to the use of solutions of low-viscosity nitrocellulose in producing the shoe-stiffener material while avoiding the troubles otherwise incident to conditioning as ordinarily with nitrocellulose solvent the shoe-stiflener blank imme diately preparatory to its being lasted as part of the shoe-upper assembly. In producing colloid-impregnated fabrics designed generally for molding to the desired shape after their colloid content has undergone resolvation, the same advantages can 'bederived as in the case of shoestiffener material by applying the inventive principles hereof. The same is also true of adhesive tapes or sheet material on which it is desired to build up in a single coatingoperation a coating of substantial thickness and uniformity from such colloidal adhesives'as cellulose derivative solutions or resin lacquers, as the use of such solutions or lacquers containing low-viscosity cellulose derivatives or resins makes possible the deposit on the fabric base of relatively thick, uniform coatings of adhesive fromi concentrated solutions or lacquers; and the subsequent adhesive-activation of the dried colloid coating or film with a solvent in the presence of the inhibitor of the development of a low-vscosity c'olloid solution does away with tendency for the activated or gelatinized coating to run away from the base and/or the surface against which the activated coating is applied.

While not limited thereto, the present invention will now be described more particularly in terms of the production of shoe-stiffener material containing nitrocellulose as its stifiening medium and the conditioning of such material in the form of the shoe-stiffener blanks in which such material is put to use. Accordant with the present invention, the usual fabric base, such as canton flannel or felt, is impregnated with a solution of low-viscosity nitrocellulose, as by passing the fabric in continuous sheet form through a bath of the solution, whereupon the impregnated sheet may be passed through squeeze rolls serving to remove excess solution therefrom and thence through a drier, e. g., the usual air-heated festoon drier. Specifically, the impregnating bath may be a solution of nitrocellulose of /2-sec- 0nd viscosity or less containing as much nitrocellulose as 38 ounces per gallon of the usual nitrocellulose solvent, say, ethyl acetate, acetone, or the like. Such a solution is quite fluent, insomuch that a. fabricsheet is impregnated substantially uniformly throughout when run continuously and at comparatively high speed through a bath of such solution of only moderate length. Indeed, the concentrated nitrocellulose solution used herein is of a fluency approximating that of a nitrocellulose solution containing only about 8 to 10 ounces of nitrocellulose of about-60 to 80- second viscosity per gallon of solvent, which latter solution must be applied as four successive impregnating baths before it carries into the fabric a nitrocellulose deposit approximating that had from a single impregnating bath of the comparatively highly concentrated nitrocellulose solution used herein.

The dried, nitrocellulose-stiffened sheet material produced as hereinbefore described with a charge of low-viscosity nitrocellulose may be cut or dried out into shoe-stiffener blanks, such as box toes, and the blanks skived at their edges, as

ordinarily. ere such blanks treated in the shoe factory as ordinarily with nitrocellulose solvent I immediately preparatory to placement in the shoe upper and lasting as part of the shoe-upper assembly, they would occasion considerable trouble, since the nitrocellulose would dissolve to form a solution of such great fluency as to migrate or flow under lasting pressure in excessive amount to the contiguous shoe-upper parts, including the lining and doubler; and, aside from the fact that the shoe stifiener proper would be'deprived of stiffening agent desired therein, there would be danger of staining the shoe-upper fabric or leather itself by such migratory or highly fluent nitrocellulose solution. In accordance with the may advantageously be added directly to the nitrocellulose solvent used for conditioning the blanks. While various solvation-inhibitors may be used herein, I have found that the metal soaps or so-called driers and other metal salts are especially effective in inhibiting the regeneration of low-viscosity nitrocellulose solutions, including lead, cobalt, zinc, manganese, aluminum, iron, and copper soaps of linoleic and linoleic acids, the corresponding metal salts of the naphthenic acids, etc. Indeed, the metal soaps or salts are so effective when added in small quantity to a nitrocellulose solvent that the operators in a shoe factory working with the shoe-stiffeners hereof containing low-viscosity nitrocellulose and with solvents containing such metal soaps or driers are entirely oblivious thereto and perform their work in exactly the same way as though they were handling the usual shoe-stifieners containing high-viscosity nitrocellulose. The practically instantaneous, Surprising effect of the lead soaps or salts on low-viscosity nitrocellulose solutions may perhaps best be appreciated from the fact that when such lead soaps or salts, which commonly contain about 34% of the metal, are added to a nitrocellulose solution of, say, /z-second viscosity in amount as little as 4%, based on the weight of the nitrocellulose, the viscosity of the solution is raised in approximately only 15 seconds to about 80 to IOU-second viscosity. It is hence understandable why the operators in a shoe factory cannot detect any differenceas between conditioning the shoe-stiffeners hereof containing low-viscosity nitrocellulose with solvents in the presence of the metallic soaps or salts and conditioning, as ordinarily, shoe-stiffeners containing high-viscosity nitrocellulose with solvents. The conditioning treatment for shoestiffeners to which reference is made herein usually involves the dipping of the shoe-stiffener in a bath of the solvent for the stifining agent present in the stiffener. Accordingly, it should be plain that because the stiffener blank is soaked with and absorbs considerable solvent,-its content .of nitrocellulose or. other colloid, if of the lowviscosity type, is in contact with suflicient solvent liquid to be resolved into an undesirable, lowviscosity or, freely fluent solution unless inhibited from such resolvation by the presence of a solvation-inhibitor pursuant to the present invention.

The invention hereof may be extended to various low-viscosity colloids other than nitrocellulose, for instance, such cellulose esters as cellulose acetate, cellulose propionate, cellulose butyrate; the various cellulose ethers, such as ethyl and methyl cellulose, that are soluble in organic solvents; and other cellulose derivatives. As in the case of nitrocellulose,- these various cellulose derivatives are available in low-viscosity form to yield in organic solvents concentrated solutions,

which, when used for coating or impregnation purposes, enable the realization of substantial coatings or impregnant deposits in a single operation; and the dried coatings or impregnant deposits may be subjected to resolvation in the pres-' of low-viscosity solutions generally from the various low-viscosity cellulose derivatives hereinbefore mentioned. There are other colloids, notably the synthetic resins, that may also be used pursuant to the present invention as concentrated solutions of low-viscosity in preparing coated or impregnated products whose resin content, after drying, is to undergo resolvation or activation for molding or other operations by the use of liquid solvents or gelatinizing agents in the presence of suitable inhibitors of low-viscosity solution formation, especially the metallic soaps or salts, which exert the desired solvation-inhibiting effect on such artificial resins as the polyvinyl resins, the polystyrol resins, the acrylate resins, etc. Accordingly, in using the term colloid in the foregoingdescription and in the appended claims, I mean to include various cellulose derivatives, artificial resins, and analogous materials that are soluble in organic solvents and that can be prevented from yielding solutions of low-viscosity, by suitable inhibitors even though they would yield such solutions in the absence tors.

The present invention is, as already indicated, of especial utility as embodied in a process wherein the low-viscosity nitrocellulose or other colloid is initially dissolved and used in concentrated solution form for coating or impregnating fabrics or other materials. It is, however, possible to use of the inhibi the low-viscosity colloid in solid form in producing the product that is to undergo after-treatment with a solvent or gelatinizing liquid for the colloid in the presence of a reagent inhibiting the formation of low-viscosity solutions. Thus, low-viscosity nitrocellulose or other cellulose derivative may be incorporated in fibrous, powdered, or precipitated form into a paperrnaking stock and the stock formed into a sheet or felt that is to undergo after-treatment with a solvent or gelatinizing liquid for the cellulose derivative in the presence of a solvation-inhibitor. Likewise, powdered cellulose derivative or artificial resin of low solution viscosity may be used in liquid suspension or as dry powder for impregnating fabrics or felts to undergo after-treatment with the appropriate solvent or gelatinizing liquid in the presence of a solvation-inhibitor. Moreover, the low-viscosity colloid to undergo the inhibited solvation treatment of the present invention as a fabric impregnant may exist in the fabric in the precipitated condition consequent to passing the freshlyimpregnated fabric through a precipitating bath before it is dried. In such latter case, the precipitated impregnating charge, e. g., precipitated nitrocellulose, is present as a disrupted or porous phase lending to the impregnated fabric high permeabilityin the solvent or gelatinizing liquid.

Considered from another aspect, it will be appreciated that the invention hereof is applicable in increasing or controlling the viscosity of an already-prepared colloid solution. Thus, the metal soaps or salts may be added to a solution oi low-viscosity nitrocellulose in amount to increase the viscosity of the solution to the desired degree. Such modification or increase of the viscosity of a solution of low-viscosity cellulose derivatives, artificial resins, or the like may be desirable when the solution is to be used as a lacquer and even for impregnating purpose. It is thus seen that the metal soaps or salts or their equivalent can be regarded as viscosity-increasing agents when added to solutions of the low-viscosity colloids. While I am unable to explain precisely how these viscosity-increasing agents function, it may be that they induce distention of the molecular structure of the colloid or restoration of the molecular structure in some measure to the micellar condition prevailing before the colloid, e. g., nitrocellulose, underwent reduction in its solution viscosity. In treating a prodnot containing the low-viscosity colloid in solid condition, for instance, as a dried residue of a solution of the low-viscosity colloid, the low-viscosity colloid does not noticeably display its original low-viscosity characteristic when treated with a colloid solvent in the presence of the metal soaps or salts or the like. Thus, a box toe blank containing the dried residue of a solution of low-viscosity nitrocellulose does not yieldat any time, so far as is observable, the original lowviscosity solution when treated with a nitrocellulose solvent in'the presence of, say, the lead or other metal soaps. n the contrary, the response of the nitrocellulose to the solvent in the presence of the lead or other metal soaps is to yield a viscous or gelatinous mass that is not readily displaced from the shoe-stiffener base and has no tendency whatever to flow away naturally therefrom. Considered in this latter light, the metal soaps or their equivalent may be regarded as solvation-inhibitors, since their function is evidently that of inhibiting the normal solvent action of the nitrocellulose solvent, perhaps by modifying the solvent power of the solvent itself or by-altering the physical nature of the colloidal solute immediately upon its dissolution in the solvent, e. g., by partially precipitating the solute as a reticular or sponge-like mass in which the solvent is absorbed as a swelling agent.

As already indicated, an important sphere of application of the present invention is in cementing or adhesively uniting bodies. For such purpose, it has heretofore been the practice to employ solutions of relatively high-viscosity colloidal adhesives, such as nitrocellulose of a viscosity upwards of about seconds, which is generally used in admixture with other colloidal adhesives or gums, e. g., gwn dammar. Thus, in the field of cement-shoe manufacture, nitrocellulose cement or lacquercontaining such high-viscosity nitrocellulose is consumed in tremendous quantity in making annually millions of pairs of shoes. It is customary to apply the nitrocellulose cement to the roughened outer surface of the insole, whereon it is allowed to dry, and to apply independently a cement coating-to the roughened marginal portion of the shoe upper to be lasted over the insole'and commonly known as the lasting allowance. are usually applied to the surface of the insole and the marginal portion of the shoe upper in order to deposit thereon through drying a cement film or stratum of a thickness enabling a realiza- Several coatings of the cement 3 tion of the desired strong bond. When the cement coatings or strata on both the insole and marginal portion of the shoe upper are completely dry, it is common practice to daub them each with such volatile nitrocellulose solvents as acetone, ethyl acetate, or the like, whereupon the freshlycolloided or adhesively activated surfaces are brought together under pressure and the outsole also applied under pressure to the adhesivecoated surfaces so as to complete the cement-' shoe assembly. Low-viscosity nitrocellulose or other colloidal adhesive have not heretofore been practicable for preparing the cement solution or lacquer to enter into the manufacture of cement shoes by reason of the fact that, while highly desirable in the initial coating of the shoe-part surfaces to be cemented or stuck together, they develop after drying and retreatment,with solvents the initial low-viscosity cement solution, in consequence of which the cement solution under the pressure exerted thereupon in lasting the upper and uniting the outs'ole to the insole is in large amount squeezed out of the regions wherein it is desired, namely, between the shoeupper margin-and the insole and between the insole-and outsole, and tends to stain the exposed upper and sole surfaces.

According to the invention hereof, the cement solution or lacquer is initially prepared at a much higher than normal concentration by using lowviscosity-nitrocellulose or other colloidal adhesive and, being freely fluent at such higher than normal concentration, is advantageously applicable in the manufacture of cement shoes, since only av single application of such cement solution to the surfaces of the shoe parts to be united is capable of depositing a dried coating or film of the requisite body or thickness. When the dried coatings or films of low-viscosity nitrocellulose or equivalent adhesive are then treated with a volatile liquid solvent containing pursuant to, the instant invention, for eirample, the metal soaps or salts, a high-viscosity cement solution is created almost instantaneously, that is, within, seconds, and the cement solution is not displaced or caused to exude unduly under the pressure incident to usual shoe-making operations, including the pressure of applying the shoe-upper margin to the insole or the outsole to the insole, from between the surfaces being adheslvely united. Not only does the invention hereof hence dispense with the need of applying multiple coatings of cement solution to the surfaces of the shoe parts to be united by the cement, but the dried deposit of cement realized in a single application of cement solution is so substantialv as to make. for

stronger bonds between the adhesively-united surfacesthan heretofore ordinarily attained by the practice of initially applying cement solutions or lacquers of high-viscosity nitrocellulose or equivalent colloidal adhesive.

I claim:

1. In a process which involves the steps of inserting into a shoe upper and lasting as part of the shoe-upper assembly a shoe-stiffener blank containing as a stiffening agent a dry nitrocellulose of downwards of about /2-second viscosity, that improvement in conditioningthe blank for said steps which comprises treating the blank with a volatile organic liquid solvent in amount sufficient to -dissolve its nitrocellulose content substantially completely, said solvent containing a metal soap of linoleic or linolenic acids in amount sufllcient to conduce to a practically instantaneous development in said blank of a nftrocellulose solution of vastly greater viscosity than that of the nitrocellulose solution developed by said solvent in the absence of said metal soap.

2. In a process involving the step of molding under pressure a fabric impregnated with the dried residue of a freelyfluent but, concentrated solution of low-viscosity cellulose derivative soluble in a volatile organic liquid solvent, that improvement in conditioning the impregnated fabric forthe moldinglstep which comprises treating the fabric with sumcient of said solvent to dissolve its content of celluldsederivative substan tially completely but in the presence of a metal salt-of the napthenic acids capable of inhibiting the regeneration of said freely fluent solution while conducing to a practically instantaneous development in said fabric of a highly viscous cellulose derivative mass.

3. In a process involving the step of molding a fabric impregnated with the dried residue of a freely fluent but concentrated solution of nitrocelluloseof a viscosity downwards of about /2- of linoleic or linolenic acids capable of inhibiting the regeneration of said freely fluent solution while conducing to a practically instantaneous development in said fabric of a highly viscous nitrocellulose mass.

4. In a process which involves the steps of inserting into a shoe upper and lasting as part of the shoe-upper assembly a shoe-stiffener blank containing a dry, low-viscosity colloid selected from a class consisting of cellulose ester and cellulose ether soluble in volatile organic liquid solvent to yield a solution of low viscosity, that improvement in conditioning the blank for' said steps which comprises treating the blank with a volatile organic liquid solvent in amount sufficient to dissolve its colloid content substantially completely but in the presence of a normally solid agent which is selected from a class consisting of the water-insoluble metal salts- 0f linoleic, linolenic, and naphthenic acids and which is conducive to the development in said blank of a colloid solution of vastly greater viscosity than that of the colloid solution developed by, said solvent in the absence of said agent.

5. In a process which involves the steps of inserting into a shoe upper and lasting as part of the shoe-upper assembly a shoe-stiffener blank containing "as a stiffening agent a dry, low-viscosity colloid selected from a class consisting of cellulose ester and cellulose ether soluble in volatile organic liquid solvent to yield -a solution of low viscosity, that improvement in conditioning the blank for said steps which comprises treating amount sufflcient to dissolve its colloid content substantially completely but in the presence of a water-insoluble metal salt of the naphthenic acids conducive to a practically instantaneous development in. said blank of a colloid solution of vastly greater viscosity than that of the colthe blank with a volatile-Organic liquid solvent in loid solutiondeveloped by said solvent in the absence of said salt.

6. In a process involving treatment of a body comprising a dryf-low-viscosity colloid with a volatile organic liquid solvent of said colloid and the manipulation of the solvent-treated body under conditions tending to cause undesirable displacement of colloid solution of low viscosity from said body, said colloid being selected from a class consisting of cellulose ester and cellulose ether soluble in volatile organic liquid solvent to yield a solution of low-viscosity, that improvement which comprisa performing said solvent treatment of, said body with sufficient of said solvent to dissolve its colloid content substantially com pletely but in the, presence of a normally solid agent which is selectecf from a class consist ng of the water-insoluble metal salts of linoleic, linolenic, and naphthenic acids and which is conducive to the development from said colloid of a solution of vastly greater viscosity than that of the solution developed by said solvent in the abiii sence of said agent; and effecting said manipulation of said solvent-treated body.

'7. In a process which involves treating a base with a freely fluent solution of \low-viscosity colloid, drying the treated base, and resolving the colloid content of the dried base with suflicient volatile organic liquid solvent to regenerate normally a freely fluent solution tending to flow away in undesirably large amount from the base, said colloid being selected from a class consisting of cellulose ester and cellulose ether soluble in volatile organic liquid solvent to yield a solution of low viscosity, that improvement which comprises resolving the'colloid content of the dried base with sufficient of said solvent to dissolve said colloid substantially completely but in the presence of a normally solid agent which is selected from a, class consisting of the water-insoluble metal salts of linoleic, linolenic, and naphthenic acids and which is conducive to the substantially instantaneous development from said colloid of a gelatinous colloid mass.

8. In a process involving the step of molding a fabric impregnated with the dried residue of a freely fluent solution of low-viscosity colloid selected from a class consisting of cellulose ester and cellulose ether soluble in volatile organic liquid solvent to yield a solution of low viscosity,

- that improvement in conditioning the impregnated fabric for the molding step which comprises treating the fabric with sufficient volatile organic liquid solvent. of said colloid to dissolve its colloid content substantially completely but ,in the presence of a normally solid agent which is selected from a class consisting of the waterfinsoluble metal salts of linoleic, linolenic, and naphthenic acids and which is capable of in-' hibiting the regeneration of said freely fluent solution while conducing to a practically instantaa gelatinous colloid mass.

9. In a process of cement-shoe manufacture involving the steps of applying a solution of colloidal adhesive to the surfaces of the shoe parts to be cemented, including the outer surface of the insole and the marginal surface of the shoe-.

upper, of drying the coatings, and of redissolving the dried coatings on said parts, before cementing said parts under pressure, with volatile organic liquid solvent, said adhesive being selected from a class consisting of cellulose ester and cellulose e'ther soluble in volatile organic liquid solvent to yield a solution of low viscosity, that improvement which comprises applying said coatings on said parts as a concentrated but freely fluent solution of low-viscosity colloidal adhesive; and redissolving the dried coatings, before said parts are cemented under pressure, with a volatile organic liquid solvent containing a normally solid agent which is selected from a class consisting of the water-insoluble metal salts of linoleic, linolenic, and naphthenic acids and which is conducive to the development from said low-viscosity colloidal adhesive of an adhesive solution of vastly greater viscosity than that of the solution developed by said solvent in the absence of said agent. v

10. In a process of cement-shoe manufacture involving the steps of applying a nitrocellulose solution to the surfaces of the shoe parts to be cemented including the outer surface of the insole and the marginal surface of the shoe upper, of drying the coatings, and ,of redissolving the dried coatings on said parts, before cementing said parts under pressure with a volatile organic liquid solvent for the nitrocellulose, that improvement which comprises applying said coatings on said. parts asa concentrated but freely fluent solution of low-viscosity nitrocellulose, and redissolving the dried coatings, before said parts are cemented under pressure, with a volatile organic STANLEY P. LOVELL. 

